Manufacturing process for filament wound thrust bearing

ABSTRACT

A process for making an individual thrust bearing assembly having an inner race and a filament wound outer race integrally formed on the inner race for rotation relative thereto and to resist axial thrust loads and the bearing made thereby. To perform the process a mandrel is provided. An inner race that includes an outer peripheral surface having a bearing quality finish and one or more annular inner race axial thrust resisting areas is mounted on the mandrel. The formation of the outer race is initiated by applying a hardenable thixotropic resin to the outer peripheral surface of the inner race to fill the annular inner race axial thrust resisting areas and to form outer race axial thrust resisting areas mating with the inner race axial thrust resisting areas. The outer race is completed by applying an overlayment of filament wound fibers on the peripheral surface after application of the thixotropic resin to provide an unhardened elongated cylindrical member having an exterior surface of desired outside dimension with the annular inner race axial thrust resisting areas filled with the thixotropic resin. The cylindrical member is hardened to form a hardened outer race wherein the annular outer race axial thrust resisting areas comprise the hardened thixotropic resin.

This is a division of U.S. patent application Ser. No. 990,420 filedDec. 15, 1992, now U.S. Pat. No. 5,360,275.

BACKGROUND OF THE INVENTION

This invention relates to bearings, and, more particularly, to a methodfor producing a filament wound thrust bearing assembly having an innerrace and an outer race integrally formed thereon and the bearing madethereby.

Thrust bearing assemblies comprise an inner member, or race having anaxis and an outer race with the inner facing bearing surfaces of theinner and outer races having at least one axial thrust resisting means,or area. To permit relative rotational movement between the inner andouter race the adjacent bearing surfaces and thrust resisting area mustbe annular. When axial thrust is to be resisted bi-directionally, thrustresisting areas must be oriented to face both axial directions.

Bi-directional thrust resisting areas can be provided by forming theouter race over an inner race that has an outer surface havingperipheral radial irregularities. The radial irregularities take theform of one or more annular troughs or grooves, or annular elevations orbeads. The inner surface of the outer race is conformed to the innerrace outer surface during formation of the outer race, and includesmating annular outer race axial thrust resisting areas mating with theannular inner race axial thrust resisting areas.

In U.S. Pat. No. 3,697,346, issued on Oct. 10, 1972, to H. B. Van Dornet al, a method of making a composite thrust bearing is disclosedwhereby a woven or braided fabric of a low friction material is appliedover the outer surface of the inner bearing member. The body of theouter bearing member is built over the low friction surface bycircumferentially wrapping resin-impregnated fiberglass over the fabric,curing and then finishing the outer member to desired axial and externalconformations. The process integrally bonds the low friction fabric tothe internal bearing surface of the outer member.

U.S. Pat. No. 4,054,337, issued on Oct. 18, 1977, to Matt et. al., andU.S. Pat. No. 4,040,883, issued on Aug. 9, 1977, also to Matt et. al.,disclose thrust bearings comprising inner and outer races having a lowfriction fabric bonded to the inner surface of the outer race through aprocess comprising building up a filament wound body over the fabric,curing and then finishing to a desired external configuration.

In known methods for producing composite thrust bearings of filamentwound outer races, the inner race outer surface grooves or the recessedareas between series of beaded elevations are filled by winding glassfilaments at a low angle at or approaching circumferential or hoopwindings. Unless such winding is used the filaments will bridge over therecessed areas which form the axial thrust resisting areas in the innerrace outer surface. If bridging occurs, the annular axial thrustresisting areas on the inner race may be incompletely filled during thefilament winding process, leaving voids which would reduce the abilityto resist axial thrust forces. The presence of or the extent of such adefect could not easily be detected after only a few winding turns ofthe filament during the winding step in formation of the outer race.

A different problem arises, however, when the annular recessed areas areintegrally filled by repeated low angled circumferential, or hoopwindings of fiberglass filaments. When hoop windings are used therecessed areas will be filled with compacted filaments oriented in thesame direction and lying in intimate contact with filaments above andbelow. Heating the fiberglass resin matrix cures the resin-fiberglassmix filling the annular recessed areas, fixing annular axial thrustresisting areas in the outer race which fill and mate with the annularinner race axial thrust resisting areas. The heat treatment of curingcauses expansion of the inner race. During curing, the outer race of thefiberglass matrix is somewhat fluid and does not become solidified untilthe elevated cure temperature is achieved. At this elevated temperaturethe relative mating axial thrust resisting areas of the inner and outerraces become fixed. Upon cooling, differential coefficients of expansioncause the steel inner race to contract more than the outer race of glassfilaments. The coefficient of expansion for the composite fiberglass andresin material occupying the peripheral recessed areas in the inner racewill approach that of the glass itself. After curing when the outer raceis fixed into a rigid form, the cooling will cause very little relativecontraction of the outer fiberglass occupying the peripheral recessedareas but will cause a relatively great contraction of the steel innerrace. The coefficient of expansion of steel is approximately 6 to 6.3times 10⁻⁶ inches/inch/°F., while the coefficient of expansion for glassis on the order of 2 times 10⁻⁶ inches/inch/°F.

Therefore, after cooling the annular outer race axial thrust resistingareas are tightly wedged within the mating annular inner race axialthrust resisting areas. This is because the coefficient of expansion ofa steel inner race is approximately three times that of the curedfiberglass-resin composition of the outer race. Thus, the greatercontraction of the steel member causes that portion of the outer memberoccupying the recessed areas of the peripheral surface of the innermember to be tightly compacted between annular thrust bearing surfaces.The wedge fit between the inner and outer members of the compositethrust bearing can become very tight, making it difficult or impossibleto have relative rotational movement along the annular peripheralsurface of the inner bearing member.

SUMMARY OF THE INVENTION

Among the objects of the invention is to provide an improved method ofproducing a composite thrust bearing having a filament wound outer raceand a metallic inner race or inner member.

Another object of the invention is to provide such a process whereby thefit between the inner and outer bearing members can be controlled.

A still further object of the invention is to provide a composite steeland filament wound thrust bearing wherein the wound filaments of thecomposite fiberglass resin outer race are orientated to bridge overrecessed areas in the peripheral surface of the inner race and do notfill the recessed areas of the annular inner race axial thrust resistingareas.

The achievement of these and other objects is provided by a methodcomprising the steps of mounting on a mandrel, an inner race thatincludes an outer peripheral surface having a bearing quality finish andone or more annular axial thrust resisting areas. A plurality of innerraces may be so mounted each including an outer peripheral surfacehaving a bearing quality finish and one or more annular axial thrustresisting means, or axial thrust resisting areas. The thrust resistingareas may comprise an annular groove or annular elevations.

Formation of the outer race is initiated by applying a hardenable highviscosity resin to the inner race outer surface to fill the recessedareas of the axial thrust resisting areas. The hardenable resin fillingthe irregularities may be thickened by combining a low viscosity resinwith a thixotroping agent to provide a resin characteristics of a gel.The formation of the outer race is then completed by applying anoverlayment of filament wound fibers on the surface of the outer race toprovide an unhardened elongated cylindrical member having asubstantially uniform exterior surface of desired outside dimension withthe radial irregularities in the bonding surface filled with thethixotropic resin. A hardenable resin is applied to the filaments tofill any interstices. The filament wound fibers are applied to bridgeover the annular grooves without displacing the thixotropic resin in theannular grooves.

The cylindrical member is hardened to form a hardened cylindrical memberand the hardened cylindrical member is finished to desired outerdimension and contour by grinding and milling. Swarf produced from thisfinishing may be mixed with the resin to form the thickened fill resinfor subsequent operations. The fiberglass swarf comprises a fillermaterial and may be added to the thixotropic resin to create a filledthixotropic resin that is then applied to the recessed areas of theannular axial thrust resisting areas. By varying the amount of swarfadded as a filler, the relative proportion of fiberglass in thethixotropic resin can be controlled. This feature can be used to choosea coefficient of expansion for cured resin forming the annular outerrace axial thrust resisting areas in the recessed areas of the annularinner race axial thrust resisting areas, and in this manner the degreeof tightness between inner and outer races in the finished bearing canbe predictably and repeatedly chosen.

When a plurality of bearings are being produced the cylindrical memberis severed at adjacent bearing interfaces, either before or afterremoval from the mandrel, to create a plurality of individual thrustbearing assemblies wherein the axial thrust resisting areas are filledby the hardened thixotropic resin in the outer race.

A layer of self-lubricating conformable material may be applied on theouter peripheral surface of the inner race to form a low frictionbearing liner having intimate conformation with the outer peripheralsurfaces and an exposed bonding surface that includes radialirregularities at the axial thrust resisting areas. This liner ofself-lubricating material preferably includes self-lubricating andshrinkable materials formed into a woven tubular sleeve that is slidaxially over the outer peripheral surfaces of the plurality of innerraces. The woven sleeve of self-lubricating and shrinkable materials isthen shrunk onto the outer peripheral surface. A low viscosityhardenable bonding resin is applied over the fabric surface to wet theexposed bonding surface and penetrate the fibers of the fabric. Thehardenable thixotropic resin is then applied to the exposed bondingsurface of the conformed bearing liner to fill the radial irregularitiestherein. The outer races are completed by applying the overlayment offilament wound fibers on the bearing liner after application of thebonding and thixotropic resins. The overlayment is cured and finishedresulting in a thrust bearing assembly having axial thrust resistingareas comprising the bearing fabric liner supported by the hardenedbonding and thixotropic resins used to fill the radial irregularities.

The thrust bearing assembly provided by the process generally comprisesan inner race including an outer peripheral surface having one or moreannular axial thrust resisting areas and an outer race conformed to androtatably mounted on the outer peripheral surface, the outer race havingannular axial thrust resisting areas in the area of its conformation tothe annular axial thrust resisting areas of the inner race. The outerrace annular axial thrust resisting areas are filled with a hardenedthixotropic resin. A major body portion surrounds the outer race annularaxial thrust resisting areas and comprises resin-impregnated filamentwound fibers bonded to the hardened thixotropic resin. A bearing linerof self-lubricating material may be conformed to and rotatably mountedon the outer peripheral surface of the inner race, the bearing linerbonded to the outer race and forming a bearing surface against the outersurface of the inner race.

Other features or advantages of the invention will become apparent tothose of ordinary skill in the art upon review of the following detaileddescription, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a winding mandrel with a series of innerraces mounted thereon and showing the external surfaces of the series ofinner races coated with a parting agent.

FIG. 2 is a perspective view the winding mandrel of FIG. 1 showing a lowfriction material applied over the external surfaces of the inner races.

FIG. 3 shows the winding mandrel of FIG. 2 in cross section and a lowviscosity resin applied over the fabric.

FIG. 4 is a cross section of the winding mandrel of FIG. 3 with highviscosity resin applied to fill radial irregularities.

FIG. 5 shows a cross section of an alternative winding mandrel whereinhigh viscosity resin is applied directly to the inner race externalsurfaces to fill radial irregularities therein.

FIG. 6 is a cross section of the winding mandrel of FIG. 4 having anoverlayment of resin-impregnated filaments applied over the fabric andhigh viscosity resin filling the radial irregularities in the fabric.

FIG. 7 is a cross section of the winding mandrel as depicted in theembodiment of FIG. 5 showing an overlayment of resin-impregnatedfilaments applied over the inner race external surfaces and the highviscosity resin filling the radial irregularities in external surfaces.

FIG. 8 is a cross section of the winding mandrel of FIG. 6 showingfinishing of the cured overlayment to a desired external dimension.

FIG. 9 is a cross section of the winding mandrel of FIG. 8 showingcutting of the finished overlayment to sever individual thrust bearingassemblies.

FIG. 10 is a partially cut away perspective view of a thrust bearingassembly severed from the mandrel of FIG. 9.

FIG. 11 is a partially cut away perspective view of an alternativethrust bearing assembly produced from an overlayment such as thatdepicted in FIG. 7.

FIG. 12 is a cross section of an alternative thrust bearing assemblyproduced using in inner race having different radial irregularitiesformed in the inner race external surface.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, the process first comprises providing amandrel 10 (FIG. 1). An inner bearing element or race 12 having an outerperipheral surface 14, opposite ends 16 and 18 and a bore 20 (FIG. 2) ismounted on mandrel 10. The inner race 12 is preferably stainless steel.The bearing outer surface 14 may comprise a bearing quality finish,preferably a corrosion protection surface such as a hard chrome orelectroplated nickel. A surface thickness of approximately 0.0005 to0.0010 inches is desirable for this purpose. In FIG. 1 a plurality ofsuch inner races 12 are mounted on a single mandrel 10, and the processwill be described in reference to using such a plurality, although thesteps of the process to be described could be applied as well to asingle race 12 mounted on a mandrel 10. Spacer elements 22 arepreferably utilized at the interfaces 21 to separate individual innerraces 12 along the mandrel 10, with said spacer elements 22 each havingan outer peripheral surface 24, opposite ends 26 and 28 and a bore 30.The outer surfaces 14 of the plurality of inner races 12 collectivelyforms a mating surface 32 for subsequent forming operations. When spacerelements 22 are used, as shown in FIGS. 1 through 9, the collectiveinner race outer surfaces 14 and spacer outer surfaces 24 together formthe mating surface 32.

Referring to FIGS. 1, 3 and 4, the bearing outer surface 14 includes oneor more radial irregularities 34 forming annular axial thrust resistingmeans, or areas 36 and 38. The irregularities 34 are preferably concaveor convex annular formations in the peripheral surface 14.Irregularities in the form of an annular groove or annular beadedelevations are preferred. Multiple irregularities 34 may be utilized toincrease thrust resistance against axial loads. The depth or height ofthe irregularities 34, as well as the number, will affect the axial loadsupporting capacity.

In the preferred embodiment shown in FIGS. 1 through 11, theirregularity 34 is a simple annular groove in the inner race externalsurface 14. Each groove has opposed facing surfaces that form theannular axial thrust resisting areas 36 and 38. With this configurationthrust loads will be supported in both axial directions, as it wouldwith an annular beaded elevation. When an irregularity 34 in the form ofan annular groove or bead is provided at each axial end of the bearingexternal surface 14, an additional advantage is found in that togetherthey may cooperate to form a seal to keep contaminants out of theintermediate bearing area intermediate the grooves.

The collective mating surface 32 is next coated with a suitable partingagent 40 (FIG. 11. Many suitable silicone materials are known for thispurpose. In the preferred process two layers of parting agent 40 arepre-applied to the inner races 12 and spacers 22 prior to assembly onthe mandrel 10. Preferably each pre-application is accomplished on allsurfaces by submersing the inner races 12 and spacers 22 in partingagent 40 and subsequently baking the components to fix the parting agent40. A sealant, not shown, may be provided between the adjoining endfaces 16 and 18 of the inner races 12, or between the inner race ends 16and 18 and spacer ends 26 and 28, when spacers are used. This sealantmay comprise a semi-liquid coating applied during assembly, or maycomprise thin compressible washers, not shown, which are assembled onthe mandrel 10 intermediate the inner races 12.

In a preferred embodiment (FIG. 2) formation of the rest of the thrustbearing is initiated by first applying a layer of self-lubricatingconformable material, or fabric 42 over the mating surface 32. Thefabric 42 comprises fibers of self-lubricating material, and preferablycomprises interwoven fibers of both self-lubricating and shrinkablematerials. A preferred fabric 42 is described in U.S. Pat. No.3,804,479, the teachings of which are incorporated herein by reference,comprising lengthwise yarns predominantly of self-lubricating fibers,such as TEFLON fibers, and circumferential yarns of a material, forexample DACRON yarn, which shrinks when heated to 300° F.

For ease of application the fabric 42 can be woven into a sleeve 44which can be slid over the mating surface 32, as shown in FIG. 1. Thesleeve 44 may be produced of any continuous length, and can be stored ona reel, not shown, until required. The length of the sleeve 44 appliedover the mating surface 44 should be on the order of 10% greater thanthe length of mating surface 44 to permit gathering of fabric 42 intothe radial irregularities (FIG. 2).

Conformation of the fabric 42 having heat shrinkable fibers isaccomplished by heating the fabric 42 to shrink the shrinkable material,which tightly conforms the fabric 42 to the mating surface 32. Analternative means for conforming the fabric 42 to the mating surface 32comprises applying the fabric sleeve 44 loosely over the mating surface32 and stretching the fabric 42 axially, which concomitantly diminishesthe circumference of the fabric sleeve 44 and thereby tightens thefabric 42 over the mating surface 32. In some cases stretching alonewill conform the fabric 42 to the mating surface 32 to sufficientdegree.

Upon conformation of the fabric 42, by whatever means, FIG. 3, thefabric 42 forms a low friction bearing liner surface 46 having intimatecontact and conformation with the mating surface 32. The bearing surface46 will constitute the load supporting surface in the completed bearing.The bearing surface 46 includes outer race axial thrust resting areas 48and 50 mating with the inner race axial thrust resisting areas 36 and38, respectively. The fabric 42 also has an outer exposed bondingsurface 52 that includes fabric radial irregularities 54 conforming tothe inner race radial irregularities 34.

A low viscosity resin 56 is applied over the fabric bonding surface 52.The resin 56 should have a sufficiently low viscosity as applied to thefabric 42 to facilitate filling the interstices of the fabric 42 bycapillary action. Epoxy resin is preferred for this purpose. The lowviscosity resin 56 only needs to coat the bonding surface 52 at theregion of the radial irregularities 52, for reasons that will beexplained in detail.

A hardenable high viscosity resin 58 is then applied, as shown in FIG.4, to the radial irregularities 54 in an amount sufficient to fillrecessed portions of the radial irregularities 54. The high viscosityresin 58 should have a paste, gel or putty-like consistency, and may beapplied to the irregularities 54 by extruding a bead of high viscosityresin 58 into the irregularities 54 while the mandrel 10 is slowlyrotated, until the volume of the irregularities 54 is completely filled.The viscosity of the high viscosity resin 58 should be low enough toallow the resin 58 to flow and completely fill the irregularities fromside to side, and yet high enough to resist exclusion from theirregularities 54 when exposed to forces of subsequent formingoperations, which will be described in detail. The initial wetting ofthe fabric 42 by the low viscosity resin 56 is necessary to establish aresin-matrix mesh between the fabric 42 and the high viscosity resin 58,as the high viscosity resin 58 will not penetrate the interstices of thefabric 42 as the low viscosity 56 resin will.

The high viscosity resin 58 may be made thixotropic by filling a lowviscosity resin 56 with CAB-O-SIL (Trademark for fire dried formedsilica S_(i) O₂ having a surface area between 200 and 400 m² /gm). Aliquid filled by such a compound is rendered thixotropic, i.e., isgel-like becoming fluid when disturbed. A thixotropic high-viscosityresin will generally be easier to apply, as it can be applied while in afluid state. The high viscosity resin 58 can be filled by mixing afiberglass scrape or swarf 80, shown in FIG. 8, resulting from grindingoperations on cured fiberglass material. Swarf may be used to affectcertain characteristics in the finished bearing in a manner to bedescribed in detail.

When the highly polished bearing surface 14 on the outer periphery ofthe inner race 12 is to be utilized as a bearing surface, with noapplication of low friction material (FIG. 5), the steps of applyingfabric 42 and low viscosity resin 56 are omitted and the radialirregularities 34 are filled directly with a high viscosity resin 58.

The completed bearings are formed by next applying an overlayment 60 ofresin impregnated filaments 62 on the inner race outer surface 14 (FIGS.6 and 7). The filaments 62 are applied to bridge over the radialirregularities 34 without filling depressions therein. The radialirregularities 34 in the bonding surface thereby remain filled with thehigh viscosity resin 58. FIG. 7 discloses filament winding directly overthe inner race outer surface 14 when no fabric 42 has been previouslyapplied.

A preferred method for applying the filaments 62 is through a filamentwinding process much as that described in U.S. Pat. No. 3,974,009, theteachings of which are incorporated herein by reference. In this methoda hardenable liquid resin 64 is supplied simultaneously with the windingof the filaments 62 (FIG. 4), by passing the filaments 62 through a bath66 of liquid resin 64 prior to winding. In FIG. 4 the resin bath 66 is acone-shaped receptacle. The filaments 62 pass downwardly through thebath 66 and through a ring which comprises the lower end of the bath 66.Preferably a plurality of filaments 62 will be oriented parallel to eachother, and will form a tape 68 of resin-impregnated filaments 62. Thebath 66 is supported on a reciprocating carriage, not shown, and byrepeated passes of the tape 68 over a rotating mandrel 10 a plurality offilament layers are applied to form the filament wound overlayment 60.The direction of the winding changes when the tape 68 nears the ends ofthe mandrel 10, and the filaments 62 are thus helically wound inoverlapping layers. The angle of wind on the mandrel 10 should be keptlarge to cause the filaments 62 to bridge over the radial irregularities54 in the process depicted in FIG. 6 and 34 in the process depicted inFIG. 7, respectively. The winding is done under tension, and a pressureis exerted by the filaments 62 on the order of 2 to 4 lbs/inch. If thefilaments 62 were applied directly into the radial irregularities 54 and34 at a low winding angle, the pressure applied by the filaments 62 willforce some of the high viscosity resin 58 from the radial irregularities54 and 34. With greater winding angles the filaments 62 bridge over theradial irregularities 54 and 34 which decreases the chance that theforce from filament winding will displace high viscosity resin 58 fromthe radial irregularities 54 and 34. With very great winding angles itmay be possible to utilize a less viscous high viscosity resin 58 thanwould be possible using narrow winding angles. When narrow windingangles are utilized a higher viscosity high viscosity resin 58 isrequired to be certain to exclude the fiberglass filaments 62 from theradial irregularities 54 and 34. Thus, the higher the viscosity of thehigh viscosity resin 58 and the greater the winding angle, the lesslikely it is that filaments 62 will enter the depressions of the radialirregularities 54 and 34.

There may be a slight swag or dip of the fiberglass filaments 62 intothe recessed portions in the radial irregularities 54 and 34. A smallamount of fiberglass 62 in irregularities is tolerable, and in fact somesmall dipping of the fiberglass 62 within the external portions of thedepressions in the radial irregularities 54 and 34 serves to strengthenthe axial stress resistance of the finished bearings.

When the winding of the overlayment 60 is completed, the tape 68 is cutand secured, providing an unhardened elongated cylindrical member 70having a substantially uniform exterior surface 72. The cylindricalmember 70 includes the filament wound overlayment 60, the high viscosityresin 58, the low viscosity resin 56 and the self-lubricating fabric 42.The cylindrical member 70 could be cured on the winding machine.Preferably, the mandrel 10 is removed from the winding machine, andhandled at its ends until curing, or hardening, of the unhardenedelongated cylindrical member 70 can be effected. Curing can be atelevated or ambient temperatures, and by any known method, such as byheating in an oven, not shown. The resin can also be heated directly,such as by infra red or high frequency radio radiation. As may berequired, the mandrel 10 can be rotated during the curing cycle toprevent dripping. The time for cure typically depends on temperature andcatalyst, when the latter is present. Curing the cylindrical member 70integrally bonds the fabric 42, resins 56 and 58, and overlayment 60together in a hardened cylindrical member 74 having bonded filaments 62extending circumferentially within (not shown). The mandrel 10 ispreferably kept within the inner races 12 to provide an arbor forsubsequent machining operations.

The hardened cylindrical member 74 is then finished, as shown in FIG. 8,to a desired outer finished dimension 76 by a grinding or machining tool78. As the depressions of the radial irregularities 54 were filled withhigh viscosity resin 58 prior to filament winding, there is a moreuniform outer dimension 72 in the unhardened cylindrical member, andthus there is less grinding necessary to form a uniform hardened outerdimension 76, (FIG. 6) and consequently less fiberglass material needsto be used in the filament winding process. The unhardened cylindricalmember 70 may be built up evenly to an as formed dimension 72 that isvery close to a desired uniform outer finished dimension 76 for thehardened cylindrical member 74, thus necessitating only a small degreeof finishing.

Swarf 80 is produced from the grinding and may be mixed with a lowviscosity resin to produce a thickened high viscosity resin for use insubsequent forming operations. Swarf 80 can be added as a filler to highviscosity resin to form a filled resin 58 for subsequent formingoperations, and the fiberglass swarf 80 may also be added to thixotropicresin to create a filled thixotropic resin.

The finished hardened cylindrical member 74 is severed at adjacentbearing interfaces 21, FIG. 9, such as by application of a cutting tool82, to separate individual thrust bearing assemblies 84. The outerdimension 76 may be finished after the bearing assemblies 84 have beenso separated. As seen in FIG. 10, the bearing assembly 84 comprises aninner race 12 having axial thrust resisting areas 36 and 38, and anouter race 86 conformed to and rotatably mounted on the outer peripheralsurface 14 of the inner race 12. The outer race 86 is bonded to thefabric 42 supporting annular axial thrust resisting areas 48 and 50mated to the thrust resisting areas 36 and 38 of the inner race 12. Amajor body portion 88 of hardened filament wound fiberglass overlayment60 is bonded to the hardened high viscosity resin 58 in the radialirregularities 54 of the fabric 42. As the filaments 60 were orientatedto bridge over the radial irregularities during filament winding, onlyhardened high viscosity resin 58 is present in the radial irregularities54. The interface of inner and outer races 12 and 86 is supported by theinner surface 46 of the bearing fabric 42. This bearing liner surface 46is conformed to and rotatably mounted on the inner race outer peripheralsurface 14, the bearing liner surface 46 having thrust resisting areas48 and 50 and supported within the inner race radial irregularities 54by hardened high viscosity resin 58. The hardened high viscosity resin60 is bonded to the fabric 42 by hardened low viscosity resin 56, and isbonded directly to the outer race major body portion 88 away from thefabric 42. At areas axially removed from the radial irregularities 34,the outer race major body portion 88 is bonded directly to the bearingfabric 42.

In the embodiment of FIG. 11, the bearing assembly 90 comprises an innerrace 12 having axial thrust resisting areas 36 and 38, and an outer race92 conformed to and rotatably mounted on the outer peripheral surface 14of the inner race 12. The outer race 92 is not bonded to fabric butrather the hardened high viscosity resin 58 filling the radialirregularities 34 of the inner race outer surface 14 forms thrustresisting areas 94 and 96. A major body portion 98 of hardened filamentwound fiberglass overlayment 60 is bonded to the hardened high viscosityresin 58 in the radial irregularities 34.

In the embodiment of FIG. 12, a bearing assembly 100 is shown havingradial irregularities formed by adjacent annular beads 102 and 104formed on the inner race outer surface 14. The beads 102, 104 defineannular axial thrust resisting areas 106 and 108 and 110 and 112,respectively. A depression 114 lies between annular axial thrustresisting areas 108 and 110, and the depression 114 is filled withhardened high viscosity resin 58. The process for producing the bearingassembly 100 is otherwise identical to that utilized in producing thebearing assembly 84 shown in FIG. 10, including the step of applyingfabric 42 over the inner race outer surface 14 prior to application ofhigh viscosity resin 58.

The advantages of the bearing assembly 84 produced by the processdescribed arises from the fact that the outer race 86 is not fixed inrigid form until the cure temperature is achieved. At this temperaturethe steel inner race 12 is expanded to the maximum level of expansion itwill achieve during cure. Upon cooling to room temperature, the innerrace 12 and outer race 86 contract from their respective expandedstates. Because the coefficient of expansion of steel is greater thanthat of glass, the inner race 12 contracts upon cooling to a greaterdegree than the fiberglass outer race 12, the latter only becoming fixedand rigid at the elevated cure temperature. Steel has a coefficient ofexpansion of approximately 0.000006 inches/inch/degree Fahrenheit, whileglass has a coefficient of expansion of about 0.0000002inches/inch/degree Fahrenheit.

Thus, when a substantial amount of fiberglass has been used to fill adepression of radial irregularities 34 of the inner race 12, uponcooling from cure temperature the greater contraction of the steel willtighten the axial thrust resisting areas 36 and 38 of the inner race 12onto intervening fiberglass fill areas of the outer race 86. The greaterthe proportion of fiberglass in the high viscosity resin 58, the greaterthe relative tightness of inner race 12 and outer race 86 in the bearingassembly 84. However, as the coefficient of expansion of resin is muchgreater than steel, approximately 0.000030 inches/inch/degree Fahrenheitfor resin, when a high proportion of resin is utilized in the highviscosity resin 58 to fill between axial thrust resisting areas 36 and38, upon cooling the cured outer race 86 the resin fill will axiallycontract to a greater degree than the steel inner race. With the presentinvention, this contraction at the axial thrust resisting areas 36 and38, results in a close tolerance running fit that allows free relativerotational movement between inner race 12 and outer race 86.

By varying the amount of swarf added as a filler, the relativeproportion of fiberglass in the thixotropic resin can be controlled,which allows predetermination of the coefficient of expansion of thefiberglass composite fill of the outer race. The swarf from grinding theperipheries of previous outer races will be a combination of fiberglassand resin. In controlling the coefficient of expansion of the resinoccupying the peripheral depressions, the relative percentage of groundglass and ground hardened resin within a given swarf should therefore betaken into account. In this manner the degree of running tolerancebetween inner and outer races may be preselected, by determiningpreferred relative coefficients of expansion of the steel inner race andthe outer race fill resin, and then selecting a fiberglass to resinratio for the high viscosity fill resin which will yield a fiberglasscomposite with the proper coefficient of expansion relative to that ofsteel. An additional advantage of utilized the grinding swarf in thismanner is that the swarf is recycled into a usable material.

From the foregoing description, one skilled in the art can make variouschanges and modifications to adapt the invention to various usages andconditions without departing from the spirit and scope of the invention.

What is claimed is:
 1. A method for making a thrust bearing assembly,said method comprising the steps of:providing an inner race including anouter surface having an annular recess; and forming an outer race aroundthe inner race by applying a layer of self-lubricating material over theouter surface of the inner race to form a low friction liner such thatthe low friction liner conforms to the outer surface of the inner raceand thereby includes a recess, extruding a flowable resin into therecess in the low friction liner, and applying an overlayment offilaments over the low friction liner and over the resin in the recessof the low friction liner.
 2. The method set forth in claim 1 whereinthe resin material is a high viscosity resin, and wherein said step ofextruding the resin is preceded by the step of adding a swarf materialto said resin.
 3. The method set forth in claim 1 wherein the annularrecess is an annular groove, wherein the filaments are resinimpregnated, and wherein said step of applying the overlayment offilaments includes the step of winding the filaments around the lowfriction liner so that the filaments bridge over the annular groovewithout displacing the resin from the annular groove.
 4. A process formaking an individual thrust bearing assembly having an inner race and afilament wound outer race integrally formed on said inner race forrotation relative thereto and to resist axial thrust loads imposedthereon during operation, said process comprising the steps of:A.providing a mandrel; B. providing an inner race that includes an outerperipheral surface having a bearing quality finish and at least oneradial irregularity forming at least one annular inner race axial thrustresisting area; C. mounting said inner race on said mandrel; D.initiating the formation of said outer race by extruding a flowable andhardenable resin into said radial irregularity to fill said radialirregularity and to form an outer race axial thrust resisting areamating with said inner race axial thrust resisting area; E. applying anoverlayment of filament wound fibers and resin on said outer peripheralsurface and on said hardenable resin to provide an unhardened elongatedcylindrical member having an exterior surface of desired outsidedimension with said annular inner race axial thrust resisting areafilled with said hardenable resin; and F. hardening said cylindricalmember to form a hardened outer race.
 5. The process according to claim4 wherein said hardenable resin comprises a thixotropic resin.
 6. Theprocess according to claim 4 wherein step D further comprises adding afiller material to said hardenable resin to create a filled highviscosity resin and applying said filled high viscosity resin to said atleast one radial irregularity.
 7. The process according to claim 4wherein, in step B, said annular inner race axial thrust resisting areacomprises an annular groove; and wherein, in step EL said filament woundfibers are applied to bridge over said annular groove without displacingsaid resin in said annular groove.
 8. The process according to claim 4and further comprising the additional steps of;finishing a cylindricalmember to a desired outer dimension and contour by grinding and millingto produce swarf; and mixing said swarf with said high viscosity resinbefore carrying out step D.
 9. A process for making thrust bearingassemblies, each of the thrust bearing assemblies having an inner race,and a filament wound outer race integrally formed on said inner race forrotation relative thereto and to resist axial thrust loads imposedthereon during operation, said process comprising the steps of:A.providing a mandrel; B. providing a plurality of inner races eachincluding an outer peripheral surface having a bearing quality finishand an annular inner race axial thrust resisting area; C. mounting saidinner races on said mandrel with adjacent inner races having aninterface therebetween; D. initiating the formation of said outer racesby applying a layer of self-lubricating material on said outerperipheral surfaces to form a low friction bearing liner conforming withsaid outer peripheral surfaces, said low friction bearing linerincluding outer race axial thrust resisting areas mating with said axialthrust resisting areas of said inner races, and a bonding surface thatincludes respective radial irregularities at said outer race axialthrust resisting areas; E. applying a low viscosity hardenable bondingresin to wet said bonding surface; F. applying a hardenable highviscosity resin to said bonding surface to fill said radialirregularities; G. applying an overlayment of filament wound fibers andresin on said bearing liner after application of said bonding resin andhigh viscosity resin to provide an unhardened elongated cylindricalmember; H. hardening said cylindrical member to integrally bond togethersaid bearing liner and said overlayment; and I. severing saidcylindrical member at each of said interfaces to create a plurality ofindividual thrust bearing assemblies each having a hardened outer race.10. The process according to claim 9 wherein said high viscosity resincomprises a thixotropic resin.
 11. The process according to claim 9wherein step F further comprises adding a filler material to said highviscosity resin before applying said high viscosity resin to saidbonding surface.
 12. The process according to claim 9 wherein in step Bsaid annular inner race axial thrust resisting area of each of saidinner races comprises an annular groove; and in step G said filamentwound fibers are applied to bridge over said annular grooves withoutdisplacing said bonding and high viscosity resins in said annulargrooves.
 13. The process according to claim 9 wherein; in step D saidstep of applying a layer of self-lubricating material includes the stepof sliding a woven tubular sleeve of self lubricating and shrinkablematerials over said outer peripheral surfaces of said plurality of innerraces; andafter step C, the process further includes an additional stepof shrinking said tubular sleeve of self-lubricating and shrinkablematerials onto said outer peripheral surfaces of said inner races. 14.The process according to claim 9 further comprising the additional stepofmixing a swarf with said high viscosity resin before carrying out stepF.
 15. A process for making a thrust bearing assembly having an innerrace and a filament wound outer race integrally formed on said innerrace for rotation relative thereto and to resist axial thrust loadsimposed thereon, said process comprising the steps of:A. providing amandrel; B. providing an inner race that includes an outer peripheralsurface having a bearing quality finish and an annular inner race axialthrust resisting area; C. mounting said inner race on said mandrel; D.initiating the formation of said outer race by applying a layer ofself-lubricating material on said outer peripheral surface to form a lowfriction bearing liner conforming with said outer peripheral surface,said low friction bearing liner including an outer race axial thrustresisting area mating with said inner race axial thrust resisting area,and a bonding surface that includes a radial irregularity at said axialthrust resisting area; E. applying a low viscosity hardenable bondingresin to wet said bonding surface; F. applying a hardenable highviscosity resin to said bonding surface of said bearing liner to fillsaid radial irregularity; G. applying an overlayment of filament woundfibers and resin on said bearing liner after application of said bondingresin and high viscosity resin to provide an unhardened elongatedcylindrical member; and H. hardening said cylindrical member tointegrally bond said bearing liner and said overlayment together to forma hardened outer race.
 16. The process according to claim 15 whereinsaid high viscosity resin comprises a thixotropic resin.
 17. The processaccording to claim 15 wherein step F further comprises adding a fillermaterial to said high viscosity resin before applying said highviscosity resin to said bonding surface.
 18. The process according toclaim 15 wherein in step B said annular inner race axial thrustresisting area comprises an annular groove; and in step G said filamentwound fibers are applied to bridge over said annular groove withoutdisplacing said bonding and high viscosity resins in said annulargroove.
 19. The process according to claim 15 wherein; in step D saidstep of applying a layer of self-lubricating material includes the stepof sliding a woven tubular sleeve of self lubricating and shrinkablematerials over said outer peripheral surface of said inner race;andafter step C, the process further includes an additional step ofshrinking said sleeve of self-lubricating and shrinkable materials ontosaid outer peripheral surface.
 20. The process according to claim 15further comprising the additional steps of;finishing a cylindricalmember to desired outer dimension and contour by grinding and milling toproduce swarf; and mixing said swarf with said high viscosity resinbefore carrying out step F.